96 PRINCIPLES OF GARDENING. [CH. II. 



and more slowly decomposing exuvias have time to 

 resolve into and accumulate soluble compounds in 

 the soil. 



The mucilaginous and saccharine mattei's formed 

 by manures, during their decomposition in the soil, 

 are unquestionably absorbed by the roots along with 

 its moisture ; for if the whole of the branches of a 

 vine or maple be cut away close to the surface of the 

 ground, it vdW continue to bleed for many days, and 

 to the last its sap will continue to afford the same 

 amomit of those matters. But their saps, and that 

 of all plants as yet sul)jected to analysis, abound 

 with cai'bonic acid gas, and there is no doubt that 

 decomposing organic manures are veiy largely bene- 

 ficial to plants by affording that gas to their roots, a 

 subject which will be further considered when we 

 are examining the phenomena attendant upon vege- 

 table decomposition. 



Of tlie less general manures, which benefit plants 

 by entering into their composition, a few words will 

 suffice. Sulphate of lime (gypsum) is a component 

 of clover, lucerne, turnips, &c. ; hence it has been 

 applied -^ith benefit to these crops, on such soils 

 as did not already contain it. Bones, broken small, 

 have lately become a very general manure; their 

 benefit, which is ver}^ permanent, is easily accounted 

 for. The bones of oxen contain about fifty per c«nt. 

 of gelatine, which is soluble in water, and rapidly 



